string_a = "this is a string."
string_b = 'This is also a string.'
python_a = 'I told my friend, "Python is my favorite language!"'
python_b = "The language 'Python' is named after Monty Python, not the snake."
python_c = "One of Python's strengths is its diverse and supportive community."

# title()首字母大写
print(string_a.title())
# lower()小写
print(string_b.lower())

# upper()大写
print(python_a.upper())
